A Novel Asymmetrical Quadrupolar Coil for Interoperability of Unipolar, Bipolar, and Quadrupolar Coils in Electric Vehicle Wireless Charging Systems

The unipolar, bipolar, and quadrupolar coils used in an electric vehicle wireless charging system are not interoperable with each other. Thus, there would be interoperability issues when the transmitting and receiving coils are not the same. To solve this issue, in this letter, we propose an asymmetrical quadrupolar coil that can be interoperable with the four conventional coils at the same position for efficient wireless power transfer, namely the unipolar coil, the bipolar coil along two perpendicular directions, and the quadrupolar coil. Large coupling coefficients can be achieved for the proposed coil with the four conventional coils when perfectly aligned. The misalignment performance with the four conventional coils is also investigated. An experimental prototype is developed to compare the conventional symmetrical quadrupolar coil with the proposed asymmetrical quadrupolar coil for validation of interoperability. The proposed asymmetrical quadrupolar coil achieves a maximum coupling coefficient of over 0.10 and a maximum dc-dc efficiency of over 85% with the four conventional coils.